Eyes opened wider, mindlessly

Daniel Dennett is clear-sighted about Darwin’s big idea, the literally “mindless” process of evolution by natural selection. Mindless doesn’t mean ignorant or foolish, though in this context it does exclude the kind of purposive intelligence that crafts clocks and watches. It’s an ingeniously clever idea, and yet blindingly obvious on reflection. “How extremely stupid not to have thought of that,” said Darwin’s self-deprecating bulldog advocate and Dennett-precursor Huxley.

If I were to give an award for the single best idea anyone has ever had, I’d give it to Darwin, ahead of Newton and Einstein and everyone else. In a single stroke, the idea of evolution by natural selection unifies the realm of life, meaning, and purpose with the realm of space and time, cause and effect, mechanism and physical law. Darwin’s Dangerous Idea

We’ll look more closely at Darwin soon, but today he’s crowding into CoPhi early to help us understand the astonishingly complex (and yet unforesighted) design of eyes and other marvels of organic nature. He and his doppelganger, our contemporary Professor Dennett.

Take the development of the eye, which has been one of the favorite challenges of creationists. How on earth, they ask, could that engineering marvel be produced by a series of small, unplanned steps? Only an intelligent designer could have created such a brilliant arrangement of a shape-shifting lens, an aperture-adjusting iris, a light-sensitive image surface of exquisite sensitivity, all housed in a sphere that can shift its aim in a hundredth of a second and send megabytes of information to the visual cortex every second for years on end.

But as we learn more and more about the history of the genes involved, and how they work – all the way back to their predecessor genes in the sightless bacteria from which multicelled animals evolved more than a half-billion years ago – we can begin to tell the story of how photosensitive spots gradually turned into light-sensitive craters that could detect the rough direction from which light came, and then gradually acquired their lenses, improving their information-gathering capacities all the while.

We can’t yet say what all the details of this process were, but real eyes representative of all the intermediate stages can be found, dotted around the animal kingdom, and we have detailed computer models to demonstrate that the creative process works just as the theory says.

All it takes is a rare accident that gives one lucky animal a mutation that improves its vision over that of its siblings; if this helps it have more offspring than its rivals, this gives evolution an opportunity to raise the bar and ratchet up the design of the eye by one mindless step. And since these lucky improvements accumulate – this was Darwin’s insight – eyes can automatically get better and better and better, without any intelligent designer.

Brilliant as the design of the eye is, it betrays its origin with a tell-tale flaw: the retina is inside out. The nerve fibers that carry the signals from the eye’s rods and cones (which sense light and color) lie on top of them, and have to plunge through a large hole in the retina to get to the brain, creating the blind spot. No intelligent designer would put such a clumsy arrangement in a camcorder, and this is just one of hundreds of accidents frozen in evolutionary history that confirm the mindlessness of the historical process.

Brilliant imperfection is the give-away. Dennett’s pal Dawkins is good at explaining eye-evolution too, as seen in yesterday’s post and in The Magic of Reality, and (through younger eyes) on stage. Dawkins explains design…

In another context, and a propos of another group discussion today, Bertrand Russell was also struck by the significance of imperfection.

When you come to look into this argument from design, it is a most astonishing thing that people can believe that this world, with all the things that are in it, with all its defects, should be the best that omnipotence and omniscience have been able to produce in millions of years. I really cannot believe it. Do you think that, if you were granted omnipotence and omniscience and millions of years in which to perfect your world, you could produce nothing better than the Ku Klux Klan or the Fascists? Moreover, if you accept the ordinary laws of science, you have to suppose that human life and life in general on this planet will die out in due course: it is a stage in the decay of the solar system; at a certain stage of decay you get the sort of conditions of temperature and so forth which are suitable to protoplasm, and there is life for a short time in the life of the whole solar system. You see in the moon the sort of thing to which the earth is tending — something dead, cold, and lifeless.

I am told that that sort of view is depressing, and people will sometimes tell you that if they believed that, they would not be able to go on living. Do not believe it; it is all nonsense. Nobody really worries about much about what is going to happen millions of years hence. Even if they think they are worrying much about that, they are really deceiving themselves. They are worried about something much more mundane, or it may merely be a bad digestion; but nobody is really seriously rendered unhappy by the thought of something that is going to happen to this world millions and millions of years hence. Therefore, although it is of course a gloomy view to suppose that life will die out — at least I suppose we may say so, although sometimes when I contemplate the things that people do with their lives I think it is almost a consolation — it is not such as to render life miserable. It merely makes you turn your attention to other things.

Other brilliantly imperfect things. Like you and me and the wonderful worlds of the stars and the cells. Just as it says in the window at Vandy’s Stevenson Science Center: “From atoms to cosmos, reaching ever into mystery.” And just as my old evolutionist friend Dr. Curtis said: this is how we keep going.

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